Koester in Dayton, Ohio

I have ben trying to find more information on my maternal grandmother's side of the family with no success. Any help would be much appreciated!!

The farthest back I got was William (Wilhelm) C Koester (Koster), born November, 1863 in Germany. He married Louise (Luise) Vogt (born Dec 1863) in 1889 in Germany. They both came to the states with their current children and settled in Montgomery County, Dayton, Ohio.

If anyone has info on this line and can help me trace it farther back, I would be thrilled!